use nix-community/impermanence module

flake.lock

@@ -1,5 +1,20 @@
 {
   "nodes": {
+    "impermanence": {
+      "locked": {
+        "lastModified": 1661933071,
+        "narHash": "sha256-RFgfzldpbCvS+H2qwH+EvNejvqs+NhPVD5j1I7HQQPY=",
+        "owner": "nix-community",
+        "repo": "impermanence",
+        "rev": "def994adbdfc28974e87b0e4c949e776207d5557",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "impermanence",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1666401273,
@@ -17,6 +32,7 @@
     },
     "root": {
       "inputs": {
+        "impermanence": "impermanence",
         "nixpkgs": "nixpkgs"
       }
     }

flake.nix

@@ -1,7 +1,8 @@
 {
   inputs.nixpkgs.url = "nixpkgs/nixos-22.05";
+  inputs.impermanence.url = "github:nix-community/impermanence";
 
-  outputs = { self, nixpkgs, ... }:
+  outputs = { self, nixpkgs, impermanence, ... }:
     let
 
       mypkgs = pkgs:
@@ -20,7 +21,7 @@
           (builtins.readDir ./pkgs));
 
       forAllSystems = f: nixpkgs.lib.genAttrs
-        [ "x86_64-linux" "aarch64-linux" ]
+        [ "x86_64-linux" ]
         (system: f system);
 
       pins = {
@@ -40,6 +41,7 @@
       mods =
         {
           inherit pins;
+          inherit (impermanence.nixosModules) impermanence;
           pkgs.nixpkgs.overlays = [ (_: mypkgs) ];
         } //
         nixpkgs.lib.mapAttrs'

hosts/levi/default.nix

@@ -1,6 +1,6 @@
 { config, pkgs, ... }:
 let
-  persist = "/var/lib/persist-${config.networking.hostName}";
+  persist = "/nix/persist";
 in
 {
   imports = [
@@ -9,12 +9,8 @@ in
 
   environment.etc = {
     "machine-id".source = "${persist}/machine-id";
-    "NetworkManager/system-connections".source =
-      "${persist}/network-connections";
   };
 
-  systemd.tmpfiles.rules = [ "d ${persist}/network-connections 0700" ];
-
   services.openssh.hostKeys = [
     { type = "ed25519"; path = "${persist}/ssh_host_ed25519_key"; }
   ];
@@ -40,6 +36,14 @@ in
     wg-home = { enable = true; path = "${persist}/wireguard_home.conf"; };
   };
 
+  environment.persistence."${persist}/system".directories = [
+    "/etc/NetworkManager/system-connections"
+    "/var/lib/nixos"
+    "/var/lib/systemd"
+    "/var/lib/upower"
+    "/var/log"
+  ];
+
   boot = {
     loader.systemd-boot.enable = true;
     loader.efi.canTouchEfiVariables = true;
@@ -51,8 +55,6 @@ in
     "/boot" = { fsType = "vfat"; device = "/dev/nvme0n1p1"; };
     "/nix" = { device = "levi/nix"; fsType = "zfs"; };
     "/home" = { device = "levi/home"; fsType = "zfs"; };
-    "/var/lib" = { device = "levi/lib"; fsType = "zfs"; };
-    "/var/log" = { device = "levi/log"; fsType = "zfs"; };
   };
 
   users.mutableUsers = false;